1. Field of the Invention
The invention relates to weld control and refers more specifically to a resistance welding control structure and method for delaying a weld until welding voltage from a source of welding energy has reached a variable preselected value or until a variable preselected number of cycles of welding energy has been checked and the voltage thereof found to be below the preselected value, wherein if welding is initiated due to the number of cycles of welding energy checked for the preselected value, a fault indicator is energized with initiation of the weld.
2. Description of the Prior Art
It is known that for acceptable resistance welding parameters such as current and voltage of welding energy must at least have minimum values. Parameters of less than minimum values result in unacceptable welds.
Further, in production welding, it is essential that the number of welds accomplished per unit time is maximized. The time between the initiation of consecutive welds should therefore be minimized for cost effective production.
It is therefore desirable to start each weld as soon as the welding energy source provides a preselected minimum parameter value. However, if the preselected minimum parameter value is not provided within a preselected time by the source of welding energy, it is usually desirable to initiate a weld with the welding energy source having a lower than desired parameter value rather than slow production down indefinitely waiting for the welding energy source parameter to attain the minimum required value. At such times, it is also desirable to energize a fault indicator to tell a welding operator that the welding parameter is not at the preselected level.
In the past, welding controls have generally been set to provide welds at predetermined intervals without regard to the particular time when the parameters of the welding energy source reach a predetermined minimum. Such systems do not assure proper welding energy parameters when welds are initiated. In fact, the welding parameters may be worse after a predetermined interval since line loading due to other equipment on the line may be worse after a predetermined interval.
Further, such controls are not capable of load scheduling. That is to say, these controls are not capable of delaying a weld if the welding energy source is, at the time a weld is scheduled, drawn down so that the parameters thereof are below desired minimum by another welder or similar load on the welding energy source.
Further, the welding controls of the past have not provided fault indicators for indicating lower than desired welding energy parameters at the initiation of a weld following a predetermined time after a weld request during which the parameters of the welding energy source are checked.